This invention relates to a mirror for SOR (synchrotron optical radiation or synchrotron radiation light).
A conventional mirror for SOR comprises a base made of a heat resistant ceramic material such as graphite or SiC and a SiC coating formed on a surface of the base by a CVD (chemical vapor deposition) method for a long period of time or at plural times, which has a predetermined thickness of several hundreds microns. The surface of the SiC coating is mirror-polished so as to become a reflection surface for SOR.
In recent years, mirrors have various increased sizes and complicated surfaces to be polished, so that the thickness of such SiC coatings must increase in order to have a desired margin for the machining purpose or the like.
However, if the thickness of the SiC coating of the mirror for SOR increases, crystal particles grow in an irregular manner in various directions. As a result, defects due to occlusion of particles or grain boundary defects resulting from irregular grain growth take place so that reflectance decreases.